Industrialised countries are heavily dependent on large centralised electricity generation plants to produce power. For example, 80% of the electricity generated in Australia is produced by coal power plants. These power plants are usually built away from the cities where the power is consumed.
In addition, secondary energy sources are becoming increasingly important. Common renewable energy sources include photovoltaic (PV) solar cells, wind turbine generators, wave turbine generators and tidal turbine generators. These sources can be connected to deliver electrical energy to the standard 50 Hz AC power distribution grid by means of AC inverter systems designed to synchronize with the power grid.
Because the secondary sources are intermittent and deliver fluctuating amounts of energy, connection to the power grid invariably requires some energy storage for ‘ride through’, with an energy delivery time frame in the order of seconds to days. Examples of storage systems include: high capacity batteries (electrical “flow batteries”), solar “molten salt”, solar hot water, and solar generated biogas where electrical energy is generated in a secondary process such as steam turbine generators. These schemes are relatively expensive and are only economically viable on large scale electrical power systems.
Referring now to FIG. 1, a typical electrical energy supply and distribution system 10, as described in our earlier patent application WO 2009/062227, comprises a supply side 20 where multiple electrical energy generators 22 are connected via connection ports 24, involving conditioning circuits 26, into a single DC electrical energy source. This energy source is supplied to a common inverter system 30 to convert it to AC for transmission on over a power grid, or other load. A rectifier 32 takes the AC power from the grid and delivers it to AC and DC loads. On the delivery side 40 energy is delivered to multiple loads 42 via connection ports 44 involving conditioning circuits 46 and other conditioning circuitry 48.
In this system the electrical energy generators 22 are connected in a series DC loop. Electrical circuit theory dictates that the current in each part of the series DC loop is the same but the voltage developed by each generator is added together. The power delivered is therefore the product of the total voltage and the loop current.
The electrical energy generators 22 include, but are not limited to: wind turbines; photovoltaic solar cells; storage batteries; ignition engine generator sets; diesel power generators; gas turbines; steam turbines; an asynchronous induction type generator and, a reticulated supply. For example, these energy source may generate powers of up to 100 kWs or MWs, and this is understood to be ‘medium scale’.